Recently, portable computing devices, such as tablet personal computers, smartphones, PDA's (Personal Digital Assistants), and electronic book readers have become widely available, most of which use touch panels as display units. Such portable computing devices often use a software keyboard, an OSK (“On Screen Keyboard”) or a screen keyboard to allow a user to operate the keyboard displayed on a touch panel to carry out input operations.
However, software keyboards offer no tactile feedback as to the location of individual keys, and correction keys on such keyboards are located far away from the “home position” that serves as a reference for key positions. Relocation of the hands to perform correction actions combined with a lack tactile feedback as to individual key locations lead to an increase in typing errors and a decrease in typing speed.